[Investigation of aerobic granular sludge cultivation by feed loading as a control strategy]

The key cultivation strategy for aerobic granular sludge cultivation was investigated using feed loading control as a main operational parameter in an aerobic/anaerobic SBR system. The results showed that the feed loading by influent COD 0-900 mg x L(-1) could effectively control the growth of sludge. The settling characteristic of inoculated sludge was important for aerobic granules formation, and its SVI 20-50 mg x L(-1) was favourable to granulation development process. Pure aeration without substrate feeding can greatly improve the settleability of sludge, and stimulate the granulation process. The activated sludge with good settleability could be converted to completely aerobic granular sludge through reducing operational loading in a certain condition. The granulation process occurred in COD feeding 400-500 mg x L(-1), and sludge concentration 8-10 g x L(-1). The developed granules were approximately 1.0 mm in diameter, SVI 25-35 mg x L(-1), settling velocity 60 m x h(-1). The authors proposed that granulation formation process was attributed to a unique operational mode in SBR system, i.e. the famine-feast alternation of substrate in reactor. The control strategy of organic loading by reducing substrate could enhance the variation of famine-feast in substrate, and made the driving force for granulation development.